As well known in the art, digital right management (hereinafter referred to as ‘DRM’) technology is a technology which manages copyright of digital works, and may be used by only an authorized user. Further, the DRM technology may limit how to use, the number of usage, duration and the like according to information such as permission limitation (condition).
The structure and the name of each object in the DRM technology are slightly different depending on various standards and commercial products, but the basic structure and operation method are very similar to each other.
The term of ‘N-screen’ is a technology or a service that one multimedia contents, e.g., movies, music and the like may be continuously enjoyed on the N number of devices. For example, the N-screen allows a broadcast or a movie being watched on TV at home to continuously watch through a smartphone or a tablet PC (or a notebook). That is, the following scenes from the last watched scene may be watched on the N number of any devices. Further, it is possible to y watch additional information, e.g., unpublished images, location/props Information and the like through the smartphone or the tablet PC.
The N-screen is a kind of cloud service that users store formally purchased multimedia contents not in their IT device but in a media sever of their own mobile carrier and access to the media server through internet when necessary. Therefore, the users may watch the multimedia contents anytime, anywhere whenever any one of the tablet PC or the smart phone.
On the other hand, when the N-screen service based on the digital rights management technology needs to be provided, some problems may occur.
The most important module in the DRM technology is a DRM agent. In order to use the protected contents, the DRM agent acquires a permission object (or license) by contacting with a rights issuer, and controls such that the multimedia contents may be used depending on the given conditions based on the acquired permission object (or license). The original contents protected by the DRM may be leaked when the DRM agent is exposed by attacks such as hacking. Therefore, it is essential that environment for safely driving the DRM agent be provided.
Because of security reasons described above, the DRM agent is typically mounted on the platform of the terminal, thus the DRM technology is dependent on the terminal. Because of characteristic in which the DRM technology is dependent on the terminal as described above, installing a new DRM agent takes a lot of work and cost. Actually, a lot of effort and time corresponding to, e.g., firmware update or operating system upgrade costs to load a new DRM agent on the platform of the terminal. Currently, dozens of standards for the DRM technologies exist. Further, if a service provider or a developer is different, developed DRM technology become also different even in the same standard, thus numerous DRM technologies currently exist.
In order to share the copyrighted contents on various terminals, the same DRM needs to be loaded on each. However, such reasons described above, i.e., increase in time and cost when installing the new DRM, which is caused by the presence of numerous DRM technologies and the terminal-dependent characteristic of the DRM makes it difficult to share the copyrighted contents through the N-screen.
The scenarios of problems which may occur when such copyrighted contents need to be shared through the N-screen is as follows. For example, Mary and John purchases smartphones in which an OMA (Open Mobile Alliance) DRM is loaded with built-in, and they would receive the N-screen service for a copyrighted educational video at home. Here, the educational video which John wants to watch is Widevine DRM-protected video, and the educational video which Mary wants to watch is Microsoft DRM-protected video. At this time, because the smartphones purchased by Mary and John and DRM formats of the educational video are different from each other, these educational videos may not be serviced through the smartphones purchased by Mary and John.
In reality, it is difficult for a manufacturer the smartphone to individually load the DRM necessary to the environment of a buyer when they release the smartphone, and also difficult for the manufacturer to additionally and separately load the DRM after the smartphone, i.e., a terminal is released. Finally, Mary and John may not receive the copyrighted educational video protected by the DRM which they want through the N-screen service.
Due to the reasons described above, the N-screen is mainly serviced for free contents that is not protected by copyright of, the N-screen is a very limitedly serviced (e.g., only if the terminal is a particular operator's service terminal and a specific manufacturer's terminal, it is possible to share the copyrighted contents) even if the N-screen is serviced for the copyrighted contents.
As the conventional technology for sharing the copyrighted contents, there are t DRM-compatible technologies such as Coral, EXIM using a DRM conversion and the like.
The DRM-compatible technologies use a conversion method based on a mediator to convert the DRM contents to fit to the DRM loaded on the terminal to which the DRM contents would be transmit. The mediator is a type of the DRM for a predetermined conversion in the EXIM. For example, supposing that the DRM A is loaded on a terminal A and the DRM B is loaded on a terminal B. In order to share the copyrighted contents received from the terminal A that is protected by the DRM A with the terminal B, the copyrighted contents need to be converted into a type of the DRM B. To do end, first, the terminal A converts (exports) contents to which the DRM A is applied into the mediator Next, the terminal B again converts (imports) the mediator converted from the contents to which the DRM A is applied into the contents to which the DRM B is applied. The conversion of the contents may be performed in each terminal and may be performed through a separate server.
The copyrighted contents may be shared using the DRM-compatible technology, but there are burdens that each operator develops the conversion technology that converts the contents into the mediator and converts the converted mediator to the contents. Further, N*N type of conversions (i.e., N*N number of conversions) are necessary to employ the numerous DRM contents and there are many limitation in employing the DRM-compatible technology. Actually, mutually reliable ways are necessary for conversion between DRMs, and when functional difference caused by the different function provided by each DRM exist, it is necessary for the reliable third object to eliminate the functional difference. Consequently, the complex conversion process of the N*N type is required.